1. Field of the Invention
The present technology relates to internal power supply circuits and semiconductor devices.
2. Background of the Related Art
In recent years, a semiconductor device, called an IPS (Intelligent Power Switch) is under development, which is obtained by integrating, into one chip, a switch element using a power semiconductor element, a driver circuit for the switch element, its peripheral control circuit, its protection circuit, and the like.
The IPS is widely utilized in vehicle electric systems, for example, such as a transmission, an engine, and a brake, and thus products achieving smaller size, higher performance, and higher reliability are desired.
As the conventional technique, there is proposed a technique of stabilizing the operation of a switch circuit by connecting an RC filter formed of a resistor and a capacitor between a frame ground and one end of a series circuit including the primary winding of a transformer and a switching element (Japanese Laid-open Patent Publication No. 09-271165).
The power supply environment of a vehicle is not good as compared with that of an ordinary home or the like, and in such an environment a high voltage, a low voltage, and/or instantaneous interruption, such as a counter-electromotive force and/or a spike, are likely to be generated. Therefore, in the IPS, an appropriate power supply control is carried out. For example, an external power supply voltage is not directly supplied to a predetermined circuit, but an internal power supply generated inside a device is supplied thereto.
Specifically, the IPS supplies a power by stepwisely increasing the voltage value of an internal power supply, such that during initial operation, the internal power supply having a voltage value lower than a power supply voltage is supplied and then after a predetermined time has elapsed, the internal power supply having the same level of voltage as the power supply voltage is supplied, and thus achieving the stabilized startup of a circuit.
However, a conventional IPS, when an abnormal current is generated, for example, due to the noise superimposed on a transmission line connected to a load, sometimes fails to normally increase the internal power supply up to a specified level.
If the internal power supply does not reach a specified level of voltage during circuit operation, then a switch for actuating a load is not able to be successfully driven, for example, due to the generation of a leakage current, thus causing a problem that a circuit malfunctions.